A suction device is commonly used for cleaning a nozzle surface of a print head. In case dirt on the nozzle surface of the print head or air bubbles in the ink chambers of the print head inhibits the accurate and reliable jetting of inkjet droplets, the nozzle surface of the print head needs to be cleaned of said dirt or of ink, in case the ink chambers of the print head are purged.
The suction device commonly comprises a suction surface which holds several suction channels, a waste ink buffer to collect sucked ink and a suction air pressure source in order to provide a suction air pressure. Before cleaning the suction surface is positioned near the surface of the nozzle surface at a predetermined height in order to provide a small gap between the nozzle surface and the suction surface. The print head is purged, whereby ink is moved from the ink chambers through the nozzles onto the surface of the nozzle surface.
By providing a suction air pressure through the suction channels in the small gap between the nozzle surface and the suction surface an air flow will be provided. The air flow will force the purged ink towards the suction channels and this flow of ink will also take away dirt from the nozzle surface on its way into the suction device.
It is important that the nozzle surface and the suction surface are accurately aligned in order that the gap between the nozzle surface and the suction surface is accurately controlled over the whole surface of the nozzle surface. This makes sure that the air flow provides an air velocity, which is substantially equal in this gap and that the surface of the nozzle surface may equally be cleaned by the suction device.
A conventional suction device is positioned near to a nozzle surface by using external positioning elements for aligning the nozzle surface and the suction surface and providing a predetermined gap. However the use of an external positioning element increases the cost of the suction device and may introduce errors into the height, the x-rotation and y-rotation between the aligned nozzle surface and the suction surface.
Alternatively a suction device may also be positioned by supporting spacers on the surface of the nozzle surface. A drawback of using spacers which are supported on the nozzle surface is that the area on the surface of the nozzle surface on which the spacers are supported cannot effectively be cleaned by the suction device. As a result dirt and ink which remain on these areas of the nozzle surface may reduce the reliability of jetting inkjet droplets from the print head.